1. Technical Field
The present invention relates to a method for judging achievability of density correction of an image and a printing apparatus.
2. Related Art
As a printing apparatus which prints an image, there is known an inkjet printer which forms dots by ejecting ink on a medium such as paper.
The inkjet printer repeats alternately the following operations: a dot formation operation in which dots are formed on a medium by ejecting ink from nozzles while a plurality of nozzle groups each consisting of a plurality of the nozzles lined up in a predetermined direction (hereinafter also referred to as a carrying direction) move in a direction intersecting the predetermined direction (hereinafter also referred to as a movement direction), and a carrying operation in which the medium is carried in the predetermined direction. Thus, an image is printed by forming dot rows consisting of dots which are lined up in the movement direction, the dot rows being formed in respective row regions which are lined up in the carrying direction.
Note that “row region” herein means a region consisting of a plurality of “unit regions” which are lined up in the movement direction. A “unit region” means a virtual rectangular region defined on a medium, and an ink droplet lands on this unit region to form the dot therein.
In such an image consisting of many row regions, there are cases in which unevenness in density occurs in a direction parallel with the movement direction. More specifically, when observing the image macroscopically, some of the row regions look darker and some of the row regions look lighter. Accordingly, this deteriorates image quality.
In order to suppress such unevenness in density, printers are proposed which stores correction values of density corresponding to the row regions and which performs density correction for each of the row regions based on the correction values during printing of an image (see JP-A-2005-224977).
The correction values are set onto the printer before shipping of the printer. It is desirable to verify whether or not density correction based on the set correction values has improved the unevenness in density at the time when the values are set.
As a method for performing such verification, there is a method of comparing degrees of unevenness in density between a comparison pattern whose density is not corrected and a comparison pattern whose density is corrected, these comparison patterns being printed by the printer to be verified. Further, it is considered to print these comparison patterns for each of the nozzle groups.
However, even in a case of a printer for which improvement effects against unevenness in density have been verified by the comparison patterns which are printed for each of the above-mentioned nozzle groups, unevenness in density may occur in an actual color image printed by the printer. In other words, there are cases in which unevenness in density which becomes conspicuous in an actual image is overlooked even through verification based on the above-mentioned comparison patterns formed with the nozzle groups. Accordingly, such a troubled printer may be shipped as a printer with which density correction is achievable.